The present invention relates to a method of feeding a cool air inlet of the cabin of an aircraft propelled by at least one jet engine and more particularly to a method in which air bled from the engine is compressed in a turbocompressor, the air compressed in this way is cooled in a heat exchanger through which air outside the aircraft is passed, the air cooled in this way is fed to a turbine stage of the turbocompressor, and the cool air inlet is fed with air leaving the turbine stage.
FIG. 1 of the accompany drawings is a diagram showing a system for feeding the cabin of an aircraft with cool air. The system is of a type known in the art. As shown here, the system 1 essentially comprises a heat pre-exchanger 2, a heat exchanger 3 and a turbocompressor 4 comprising a turbine stage 5 and a compressor 6.
The pre-exchanger 2 is connected to an inlet 7 for air bled from a compression stage of a jet engine propelling the aircraft when the latter is flying at cruising speed. This air is routinely at a temperature of several hundred degrees and is cooled in the pre-exchanger 2 by a stream of air which is taken from outside the aircraft via an air intake 8 feeding a chamber of the exchanger and evacuated via an outlet 9 of that chamber.
The air bled from the engine leaving the pre-exchanger 2 is sufficiently cooled to enter the compressor 6, which is routinely made of light alloy. The compressed, and therefore heated, air which leaves the compressor 6 is cooled again in the exchanger 3, by the same flow of outside air between the intake 8 and the outlet 9, so that its temperature is substantially reduced to that of the flow of outside air.
The air leaving the exchanger 3 then enters the turbine stage 5 which drives the compressor 6. As the air expands in the turbine stage its temperature falls to a relatively low value, of the order of 3xc2x0 C., for example, suitable for feeding it to the cool air inlet 10 of the cabin 11 of the aircraft (part of which is shown diagrammatically in FIG. 1) with no risk of the pipes through which it flows icing up.
The cool air at 3xc2x0 C. delivered to the cabin is mixed with the air in the cabin to cool it. The cabin air pressure is regulated by one or more valves 12 which are part of a system for pressurizing the cabin 11 and allow some of the air in the cabin to escape from it.
Part of the fuel consumption of the jet engine from which the air is bled to feed the system described above is obviously associated with bleeding the air in this way. The difference xcex94T between the temperature of the air entering the cabin (approximately 3xc2x0 C.) and the temperature of the air in the cabin (approximately 20xc2x0 C.) is relatively small (approximately 17xc2x0) and makes it necessary to choose the dimensions of the system so that it can supply a relatively high flow of cooled air to the cabin, which adds to the overall size, weight and consequently manufacturing cost of the system.
An object of the present invention is to provide a method of feeding a cool air inlet of the cabin of an aircraft adapted to be used with a system for reducing the fuel consumption of the engine from which the system bleeds compressed air, the system also being lighter, more compact and less costly to manufacture than the prior art system described in the preamble of this description.
The above object of the present invention is achieved with a method of feeding a cool air inlet of the cabin of an aircraft propelled by at least one jet engine, of the type described in the preamble of this description, and in which mechanical energy is extracted from the air leaving said cabin of the aircraft, said mechanical energy is injected into said turbocompressor by means of a second turbine stage coupled to the first turbine stage, and cooling energy is additionally extracted from said air leaving the cabin of the aircraft, which method is noteworthy in that the cooling energy extracted in this way is injected into the cooled air leaving the exchanger downstream of the compressor with the aid of a second heat exchanger and a third heat exchanger located respectively upstream and downstream of said second turbine stage.
As described in detail later, the above method delivers to the cabin air which is at a lower temperature, and which can therefore have a lower flowrate, than that delivered by the FIG. 1 system, which is beneficial in terms of the fuel consumption of the jet engine from which the air is bled and from the point of view of the weight, overall size and therefore cost of manufacture of the system for implementing the method according to the invention.
That system, which includes an inlet for air bled from the engine, a turbocompressor including a turbine stage and a compressor fed with the air bled from the engine, an exchanger fed with the air leaving said compressor to cool said air with the air of a flow of air outside the aircraft, the cooled air outlet of the exchanger feeding said turbine stage, a second turbine stage coupled to the first turbine stage and fed with air extracted from the cabin of the aircraft, means fed with the air extracted from the cabin for cooling the air bled from the engine and leaving the exchanger, being noteworthy in that said means include a) a second heat exchanger for heating the air coming from the cabin and delivered to the second turbine stage and for cooling the air bled from the engine and leaving the first heat exchanger and b) a third heat exchanger for heating the air leaving the second turbine stage and for cooling the air bled from the engine.
Other features and advantages of the present invention will become apparent on reading the following description and examining the accompanying drawings.